Method of gold plating steel and ferrous alloys



Passed J....1,- 941 12 227,454

yUNlTED STATES PATENT "'o F1 Joseph B. Kusimer, New York, N. Y.,assignor to Benjamin Robinson, New York, N. Y.

No Drawing. Application November 11, 1937, Serial No. 174,054

3 Claims. (M. N L-12') This invention relates to an improved method inthe gold plating bath and the platingoperator plating gold on steel andferrous alloys, the tion commenced. The preferable gold plating objectbeing to produce a methodwhereby gold bath consists of the followingingredients in apmay be plated directly on steel, iron, and otherproximately the following proportions:

5 desired ferrous material in a way to be securely I Grams united withthe article being plated. Potassium cy 100 5 In carrying out theinvention it has been found Potassium carbonate 80 that certainsolutions hereinafter fully set forth Potassium gold cyanideaui A- 20must be used to properly cleanse a metal article Ammonium benzoate a 2.5m oi oxide. It also has been found that the plating $odium form l- 2.5

solution must contain a special reagent to inhibit the free acidremaining on the metal from at- Water make l tacking the surface of themetal during the plat- It will be noted that the ammonium benzoate ihgoperation. and sodium formate are reagents and act to pre to Whenplating an article of steel or ferrous alvent too rapid plating. Theseinhibitors are deloy, the article is first thoroughly cleaned of allsirable to cause a fine solid plating to be secured. ordde and is alsoetched to a certain extent, It will therefore be seen that theformateand namely, until a line etched surface is secured, so henzoate in theDI D Set with lower the as to present an appreciably greater area towhich oxidizing effect of the free cyanide on the article no the goldmay cling. More specifically, in carrybeing plated by depressing the CNionization. The

ing out the method the article is first cleansed in gold has thereforethe opportunity of being dea suitable alkaline cleanser. -The article isthen posited on the surface of the article before 'a dipped in a specialbath to remove all oxide film tarnish film can be formed on it. from thecleansed article. The desired bath for As eq iv lents for h en s nd theother W this purpose is set forth in the following formula: gold platingsalts the following could be used;

By volume I KAuCna NaAu(CN)2 I Parts or NH4Au(CN)2 llythoduosilicle acid(concentrated), KrCOa NazCOs m 50 to 100 g or NHiCOs so l-lydrofluoricacid HF 5 KCN NaCN Water (distilled), H20 25 to 50 sum 1 t or NHMCN) Asubstitute for the acid hydrofluosilicic could Pmssmm mate 1H? fluoboricacid or the acids of the combination I or Ammonium mrmate all offluorine and the silicon earth group. Acids of g fi bemoate} orPotassium benzoate 35 this type, while sufilciently strong to destroythe oxide film on steel do not appreciably aflect the It will, ofcourse, be understood that the artiunder surface during a short exposureto them, cle may be submerged in the plating bath as and are thereforealso suitable for the purpose of long as desired with the full currentflowing. w the present invention. For an extremely light plating coatfive or six 40 The article to be plated is dipped in the above secondswould probably be satisfactory but ususolutlon to secure the removal ofthe oxide fllm. ally the article 'is left in the bath for a longer Thisdipping operation may be from 30 seconds time, as, for instance,one-hall hour or longer to 2 minutes according to the amount of etchingwith a current from 1 to 6 volts As the sur- 4,5 desired as the solutionwill not only remove the face is clean and is also formed with fineetch- 4 oxide film but will etch the surface of the article ing, thegold deposited on the article will interto be plated. This dipping maybe done by ordilock with the etched surface and form substannary dippingor current maybe used and caused tially an integral part thereof so thatthe plated to pass through the article during the dipping article may bebrushed or buffed, or polished in to operation. This will produce astronger etching any desired way and without becoming loose or eflect.in any way injured.

After the article has been dipped as Just'de- I claim: scribed it isimmediately immersed in clean water, 1. The method of electroplatinggold on ferw ich m y be o Arter quic dippin the rous metals consistingin cleaning the article to 65 article in clean water it is immediatelyimmersed be plated in an alkaline bath, subjecting the herent state.

2. The method of plating gold on steel and ferrous alloy articlesconsisting in subjecting the article to a mild ionized acid bath untilall of the oxide on the article has been removed and the surface of thearticle has been attached sufiiciently to enlarge its surface by a veryfine etched surface, washing the article in water and immediatelysubjecting the article to an electroplating action in a plating bathcontaining potassium cyanide, potassium carbonate, potassium goldcyanide and a reagent consisting of ammonium benzoate and sodium for-,mate acting to cause the lowering of the attacking effect of the freecyanide on the article by depressing the ionization to permit the goldto be deposited on the surface of the article before a tarnish film canform.

3. The method of gold plating an article of ferrous material on which anoxide film normally forms which includes subjecting the article tohydrofluosilicic acid until the oxide film has been removed and anetching operation has taken place to increase the surface, andelectrolytically depositing a gold plate on the etched article from acyanide plating bath containing ammonium benzoate and sodium formate.

JOSEPH B. KUSHNER.

